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A simple, green and efficient solventless procedure for the synthesis of eleven dihydropyrano[3,2-b]chromenediones from the three-component condensation reaction of kojic acid, aromatic aldehydes, and dimedone using a reusable alum as catalyst is described. Neste trabalho é descrito um procedimento livre de solventes, limpo, simples e eficiente para a síntese de diidropirano[3,2-b]cromenodionas (onze derivados) a partir da reação de condensação de três componentes de ácido kójico, aldeídos aromáticos e dimedona, utilizando alume como catalisador reutilizável.

An environmentally friendly procedure for the preparation of 10-aryl-6,8-dimethyl-6,10-dihydro-5-oxa-6,8-diazaanthra[2,3- d ][1,3]dioxole-7,9-diones under thermal solvent-free conditions in the presence of cyanuric chloride as heterogeneous catalyst was developed.

FeCl3–SiO2 is environment-friendly heterogeneous catalyst for the condensation of kojic acid and aldehydes with dimedone to afford dihydropyrano[3,2-b]chromenediones. The solid acid catalyst is stable and can be easily recovered and reused without appreciable change in its efficiency.

To develop a new facile protocol for the synthesis of 2′-aminobenzothiazolo-arylmethyl-2-naphthol derivatives, N-bromosuccinimide (NBS) was used as an efficient catalyst for the one-pot synthesis of 2′-aminobenzothiazolo-arylmethyl-2-naphthols in excellent yields fromβ-naphthol (1 mmol), aromatic aldehydes (1 mmol), and 2-aminobenzothiazole (1 mmol) at 60°C under solvent-free conditions.

Ferric chloride on silica is used for the condensation of kojic acid, dimedone, and aromatic aldehydes under neat conditions.

An environmentally friendly procedure for the preparation of 10-aryl-6,8-dimethyl-6,10-dihydro-5-oxa-6,8-diazaanthra[2,3- d ][1,3]dioxole-7,9-diones under thermal solvent-free conditions in the presence of cyanuric chloride as heterogeneous catalyst was developed.